[BPO]

This should be pretty interesting! List them any way you like.

Here are my most used and best liked:

Linux:
XEphem
CdC
KStars


Windows - Planetarium:
HNSky (Hallo northern sky)
CdC
WinStars
Stellarium


Windows - Other:
EQASCOM
Deep-Sky Planner
GuideDog
MaxIm DL